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99 Max P0505 - IACV good but Low Connector Volts - Wiring Harness or Battery Cable?
Starting a new thread for this specific issue, but if you're up for a good read, check my other posts for my "journey" to this point ...
The problem is the P0505 Code for the IACV, which makes sense because after everything I've done to this car, I still have idle problems.
Car starts, runs, accelerates great, and I get trouble codes, so I'm assuming the ECU is operational at least. The battery is only a couple years old but still tests over 12V cold. IACV is a cleaned-up junkyard replacement - tested the pins for continuity with multimeter, all good there, and I removed the plunger portion, cleaned, and tested by turning the key off & on to make sure the plunger moved in & out and it did. Original gasket looked good so just re-used it. Only obvious problem is when I tested the CONNECTOR for voltage, both pins 2 & 5 showed only about 8.5V, definitely not the battery voltage,which the FSM says it should be.
Then it says it should be a short or open circuit in the harness. I've spent ALOT of time reading, researching & getting sidetracked - all to figure out my basic problem is that somewhere the power supply between the battery and the IACV is not getting through. The FSM suggests the area between the IACV and ECCS relay, to check connectors E14 & F37. I have the wiring diagram BUT I'm having trouble applying the diagram to the actual wiring I see in my car to know where that relay & those connectors are in reality.
With some guidance, I'd like to figure out if it's just one wire for this one component that's bad, but I would need to figure if any other components are being affected (no other codes or symptoms, so it doesn't seem like it).
Logic would seem if the battery cables were the culprit, I'd be having more issues/problems, and my thoughts are if I can pinpoint a bad wire, I can just run a new external one, rather than disrupt the main wiring harness. About 80% of what I've read about re-using the IACV gasket, says it's ok to do, plus, that has nothing to do with the connector voltage anyhow.
Any suggestions? Advice? Should I just find a good used main harness? Are they pretty straight forward to replace? Will I need to do anything with the ECU if I put a new electrical harness in?
Don't go off the deep end and replace the wire harness - at least yet. It is a possibility but the probability is at best a tenth of a percent. You have a 99.9 % chance it is something else. And if you did take on this PITA of a job, you would not have to do anything to the ECU.
If the wire going to pins 2 & 5 of the IACV connector were open, you would get a reading of 0 (zero) volts. If the wire were to be shorted, you would get a reading of 0 (zero) volts and have a blown fuse.
Having partial voltage could be a dirty/corroded connection in the wire that brings the 12 volts to the IACV. It could also be the way the voltmeter was connected, specifically what the voltmeter negative lead was connected to.
The ECCS relay is in the box in front of the battery. It is in the front row towards the grille, all the way on the end next to the radiator. I think the label on the cover calls it ECM Relay. Reference page EL-312, lower right corner.
The wire harness plugs E14/F37 are by the fuse panel next to the battery. There is a wire bundle coming out of the rear (towards the firewall). After a little bit, there are 2 same size connectors coming out of that thicker wire bundle. They are both 8 wire connectors; one is brown in color and the other is black. E14 is the black one. Reference page EL-318, co-ordinates F3.
Thank you very much DennisMik - exactly the help I needed!
I agree on not rushing to replace the whole harness, but if need be, I can handle another PITA job, slow & steady, but I'd rather not have to. I've also read it's very rare that it's the main harness, but there is a TSB out there for my vehicle for breakage in the main harness by the right, passenger strut tower - I question if the repair/preventative measures were done on mine or not.
I have tomorrow to dive into this so I will try different negative lead connections with the multimeter, and check out the relay & other two connectors. I downloaded the FSM to my hard drive well over a year ago so thanks for the links, but I should be good to go now! Your helping me locate these items and pointing out the voltage issue is exactly what I needed to march ahead, so I'll post back with an update soon! Cheers - Jen
Not finished yet but had to share a small ah-ha moment ... took out that EFI relay and can see actual burn marks on pin #7 ... pulled adjacent, identical relay for the fan and all its pins were beautiful. Gonna grab a new relay at AZ for less than $20, replace it, and give things a whirl...
Burnt at base of #7 pin ... original EFI relay ... BAD!
Not finished yet but had to share a small ah-ha moment ... took out that EFI relay and can see actual burn marks on pin #7 ... pulled adjacent, identical relay for the fan and all its pins were beautiful. Gonna grab a new relay at AZ for less than $20, replace it, and give things a whirl...
Burnt at base of #7 pin ... original EFI relay ... BAD!
Jen,
You might have oxidation in the relay, and on the contacts.
If any contacts look oxidized, some contact cleaner and a bit of 600 grit sandpaper can make them shine.
Oxidation reduces how much electrity can flow. Thus can reduce voltage.
You could swap that relay with the one next to it or above it and drive the car. If you have a bad relay in the radiator fan spot, you might never notice it until summer time.
10-08-2016, 11:18 AM
